I have been learning for a year and seem to be going the same route just seems my driving not as good as it was when I was with another instructor but I moved out of the area.
If you are aren't happy with the one you are using then go for a different one, but it's worth asking around locally for recommendations before doing it.
Do you get practice away from these lessons or is that the only time you get to drive? It is probably rather a lot, surely they have told you why you're not ready for your test and what needs more work?
A lesson approx every three weeks is not going to do you much good (if that is the only practice you get). You're going to be rusty every time you get in the car and probably take half a lesson to warm up.
Far better if you had had 18 lessons in 18 consecutive weeks. Practice makes perfect.
Maybe you need to turn up for the lessons and you might learn quicker. You said recently that you cancelled your lesson and took dog out for walk instead.